[gcc r15-5725] c: Do not remove _Atomic from array element type for typeof_unqual [PR117781]

[Joseph Myers via Gcc-cvs]

https://gcc.gnu.org/g:eaa675ad3f0a033537440f93172a7b122c04cab5

commit r15-5725-geaa675ad3f0a033537440f93172a7b122c04cab5
Author: Joseph Myers <josmy...@redhat.com>
Date:   Wed Nov 27 14:10:37 2024 +0000

    c: Do not remove _Atomic from array element type for typeof_unqual 
[PR117781]
    
    As reported in bug 117781, my fix for bug 112841 broke the case of
    typeof_unqual applied to an array of _Atomic elements, which should
    not have _Atomic removed since only the element type is atomic, not
    the array type.  Fix with logic to ensure that atomic element types
    are preserved as such, while other qualifiers (i.e. those that are
    semantically rather than only syntactically such in C) are removed.
    
    Bootstrapped with no regressions for x86_64-pc-linux-gnu.
    
            PR c/117781
    
    gcc/c/
            * c-parser.cc (c_parser_typeof_specifier): Do not remove _Atomic
            from array element type for typeof_unqual.
    
    gcc/testsuite/
            * gcc.dg/c23-typeof-5.c: New test.

Diff:
---
 gcc/c/c-parser.cc                   | 16 +++++++++++++---
 gcc/testsuite/gcc.dg/c23-typeof-5.c | 18 ++++++++++++++++++
 2 files changed, 31 insertions(+), 3 deletions(-)

diff --git a/gcc/c/c-parser.cc b/gcc/c/c-parser.cc
index 47668eceeded..730f70bfdc66 100644
--- a/gcc/c/c-parser.cc
+++ b/gcc/c/c-parser.cc
@@ -4443,9 +4443,19 @@ c_parser_typeof_specifier (c_parser *parser)
   parens.skip_until_found_close (parser);
   if (ret.spec != error_mark_node)
     {
-      if (is_unqual
-         && TYPE_QUALS (strip_array_types (ret.spec)) != TYPE_UNQUALIFIED)
-       ret.spec = TYPE_MAIN_VARIANT (ret.spec);
+      if (is_unqual)
+       {
+         bool is_array = TREE_CODE (ret.spec) == ARRAY_TYPE;
+         int quals = TYPE_QUALS (strip_array_types (ret.spec));
+         if ((is_array ? quals & ~TYPE_QUAL_ATOMIC : quals)
+             != TYPE_UNQUALIFIED)
+           {
+             ret.spec = TYPE_MAIN_VARIANT (ret.spec);
+             if (quals & TYPE_QUAL_ATOMIC && is_array)
+               ret.spec = c_build_qualified_type (ret.spec,
+                                                  TYPE_QUAL_ATOMIC);
+           }
+       }
       if (is_std)
        {
          /* In ISO C terms, _Noreturn is not part of the type of
diff --git a/gcc/testsuite/gcc.dg/c23-typeof-5.c 
b/gcc/testsuite/gcc.dg/c23-typeof-5.c
new file mode 100644
index 000000000000..e8076982822d
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/c23-typeof-5.c
@@ -0,0 +1,18 @@
+/* Test C23 typeof and typeof_unqual on arrays of atomic elements (bug
+   117781).  */
+/* { dg-do compile } */
+/* { dg-options "-std=c23 -pedantic-errors" } */
+
+_Atomic int a[2], b[2][2];
+const _Atomic int c[2], d[2][2];
+
+extern typeof (a) a;
+extern typeof (b) b;
+extern typeof (c) c;
+extern typeof (d) d;
+extern typeof_unqual (a) a;
+extern typeof_unqual (b) b;
+extern typeof_unqual (c) a;
+extern typeof_unqual (d) b;
+extern typeof_unqual (volatile _Atomic int [2]) a;
+extern typeof_unqual (volatile _Atomic int [2][2]) b;